I'll be happy to benchmark, we already have code to test the multi-client hitting 1 region server case.
J-D On Wed, Jan 13, 2010 at 10:38 AM, Dhruba Borthakur <dhr...@gmail.com> wrote: > I will try to make a patch for it first. depending on the complexity of the > patch code, we can decide which release it can go in. > > thanks, > dhruba > > On Wed, Jan 13, 2010 at 9:56 AM, Jean-Daniel Cryans > <jdcry...@apache.org>wrote: > >> That's great dhruba, I guess the sooner it could go in is 0.21.1? >> >> J-D >> >> On Wed, Jan 13, 2010 at 8:51 AM, Dhruba Borthakur <dhr...@gmail.com> >> wrote: >> > I opened http://issues.apache.org/jira/browse/HDFS-895 for this one. >> > >> > thanks, >> > dhruba >> > >> > On Tue, Jan 12, 2010 at 9:41 PM, Joydeep Sarma <jsensa...@gmail.com> >> wrote: >> > >> >> this is internal to the dfsclient. this would explain why performance >> >> would suck with queue threshold of 1. >> >> >> >> leave it up to Dhruba to explain the details. >> >> >> >> On Tue, Jan 12, 2010 at 9:16 PM, stack <st...@duboce.net> wrote: >> >> > On Tue, Jan 12, 2010 at 9:12 PM, stack <st...@duboce.net> wrote: >> >> > >> >> >> > any IO to a HDFS-file (appends, writes, etc) ae actually blocked on >> a >> >> >> > pending sync. "sync" in HDFS is a pretty heavyweight operation as >> it >> >> >> stands. >> >> >> >> >> >> i think this is likely to explain limited throughput with the default >> >> >> write queue threshold of 1. if the appends cannot make progress while >> >> >> one is waiting for the sync - then the write pipeline is going to be >> >> >> idle most of the time (with queue threshold of 1). >> >> >> >> >> >> i think it would be good to have the sync not block other writers on >> >> >> the file/pipeline. logically - it's not clear why it needs to (since >> >> >> the sync is just a wait for the completion as of some write >> >> >> transaction id - allowing new ones to be queued up subsequently). >> >> > >> >> > >> >> > Are you talking about internal to DFSClient Joydeep? Or some >> >> > synchronization block up in hlog? >> >> > >> >> > St.Ack >> >> > >> >> >> > >> > >> > >> > -- >> > Connect to me at http://www.facebook.com/dhruba >> > >> > > > > -- > Connect to me at http://www.facebook.com/dhruba >
